This is where your ignorance shines through and blinds me.
The Z06 is not "beating" Lamborghinis, Ferraris, or Porsches.
Also, America has been in the super car race for much longer than since the Z06 came out.
Maybe you should check out the Callaway Sledgehammer sometime... The "fastest" car... And something even funnier, the person who started the company you are blabbing about as well (Lingenfelter) DROVE IT HIMSELF TO SET THE RECORD.
Oh, and by the way, this was based on a C4 Corvette... long before the Z06 came out.
Then, as Jman mentioned, there's also Vector, Mosler, Vision, Cunningham, Saleen, etc.
Shit, Vector's entire purpose was to set the speed record.